So I did an oil change today and with the ice in my lot and whatnot things didn't go as smoothly as I would have liked and then to top things off I forgot to fill my WIX sample bottle with the stream of the oil draining. I went from an 8K to 9K run so I definitely want to get the TBN results so I filled the bottle from the drain pan. Although the pan had been drained, it is well used and wasn't wiped clean. Will the TBN reading be accurate? Should I skip this drain and go 9K again? What would you do?